WO2013108379A1

WO2013108379A1 - Control device for internal combustion engine

Info

Publication number: WO2013108379A1
Application number: PCT/JP2012/050953
Authority: WO
Inventors: 典昭熊谷; ▲吉▼岡　衛
Original assignee: トヨタ自動車株式会社
Priority date: 2012-01-18
Filing date: 2012-01-18
Publication date: 2013-07-25
Also published as: US9222387B2; JPWO2013108379A1; EP2806127A4; JP5790790B2; EP2806127A1; CN104053875A; CN104053875B; EP2806127B1; US20140352283A1

Abstract

A control device for an internal combustion engine, comprising an electric heating catalyst for heating an exhaust-purifying catalyst by heat from a heat-generating body which generates heat by the supply of electricity, the control device also comprising: a determination means for determining the amount of fed energy suppressed by the exhaust to the electric heating catalyst, so that a heat-generating body internal temperature difference, which is the temperature difference between predetermined regions of the heat-generating body of the electric heating catalyst, remains within a predetermined temperature range during cold startup of the internal combustion engine; and a control means for controlling the operating state of the internal combustion engine in accordance with the suppressed amount of fed energy determined by the determination means. The occurrence of cracking in the heat-generating body of the electric heating catalyst is minimized by this configuration.

Description

Control device for internal combustion engine

The present invention relates to a control device for an internal combustion engine.

In a filter provided in an exhaust system of an internal combustion engine for collecting and removing particulates (PM) in the exhaust, generally, the collected PM is oxidized and removed, so that the PM collecting ability of the filter is obtained. Is maintained. As described above, when the collected PM is oxidized and removed in the filter, a rapid temperature gradient is generated in the filter due to heat generated by the oxidation reaction, which may cause cracking or melting of the filter. Therefore, for example, a technique described in Patent Document 1 has been developed as a technique for suppressing the occurrence of cracks in a filter. In this technique, in order to reduce the temperature gradient in the filter during PM oxidation, the average temperature increase rate in the filter is 100 ° C./min or less in the region where the average temperature of the filter is 100 ° C. to 700 ° C. In addition, the oxidation condition of PM in the filter is adjusted.

As shown in Patent Document 2, a sensor for detecting a desired parameter is provided in an exhaust system of an internal combustion engine, and a heater for heating the sensor for the purpose of increasing the detection accuracy of the sensor or the like. May be added. In this case, when moisture is attached to the sensor when the sensor is heated by the heater, the sensor may crack due to a temperature difference between the heated sensor side and the moisture side. Therefore, Patent Document 2 discloses a technique for gently controlling the heating of the sensor by the heater so that the temperature difference between the inside of the heater and the surface does not exceed a predetermined value.

JP-A-9-287433 JP 2004-360526 A

In order to effectively purify the exhaust from the internal combustion engine, an electrically heated catalyst may be provided in the exhaust passage. This electrically heated catalyst enables rapid activation of a catalyst having exhaust purification ability by heat from a heating element that generates heat by supplying power. Unlike the sensor provided in the exhaust system shown in the prior art, the electrically heated catalyst is intended for exhaust purification, so that the exhaust from the internal combustion engine flows into the electrically heated catalyst. ing. Therefore, it becomes a structure which can receive much energy from the exhaust_gas | exhaustion which flows in. As a result, there exists a possibility that the temperature difference which causes a crack may arise in the heat generating body of an electrically heated catalyst due to the said energy.

In particular, at the time of cold start of the internal combustion engine, the temperature of the electrically heated catalyst itself is relatively low, and therefore the applicant of the present invention is likely to cause a temperature difference in the heating element that causes cracks. I found it. Therefore, it is inferred that it is necessary to appropriately control the thermal energy received from the exhaust gas flowing into the electrically heated catalyst at the time of cold start of the internal combustion engine. However, in the prior art, the necessity has been sufficiently studied. Absent.

The present invention has been made in view of the above-described problems, and in an internal combustion engine including an electrically heated catalyst, a temperature difference that causes cracks does not occur in the heating element that generates heat when energized in the electrically heated catalyst. Another object of the present invention is to provide a control device for an internal combustion engine that appropriately controls the operating state of the internal combustion engine.

In the present invention, in order to solve the above-mentioned problem, when the internal combustion engine is cold-started, energy that is discharged from the internal combustion engine and creates a temperature difference in the heating element of the electrically heated catalyst is supplied to the catalyst via the exhaust gas. And the relationship between the operating state of the internal combustion engine. As a result, it is possible to effectively generate cracks in the heating element during a cold start of the internal combustion engine, taking into account that the energy of the exhaust, that is, the energy input to the electrically heated catalyst, varies according to the operating state of the internal combustion engine. Can be suppressed.

More specifically, the present invention relates to an internal combustion engine control device that is provided in an exhaust passage of an internal combustion engine and heats a catalyst having an exhaust purification capability by heat from a heating element that generates heat by supplying power. The electric heating type so that a temperature difference in the heating element, which is a temperature difference between the catalyst and the predetermined part of the heating element of the electric heating catalyst at the time of cold start of the internal combustion engine, falls within a predetermined temperature range. Determining means for determining an amount of suppression of input energy via exhaust to the catalyst, and control means for controlling an operating state of the internal combustion engine according to the amount of suppression of input energy determined by the determination means. Prepare.

In the electric heating type catalyst provided in the internal combustion engine, the heating element is heated by supplying electric power (energization) to the heating element, and the catalyst having the exhaust purification ability is heated by the heat. As an example, a form in which the catalyst is supported on a carrier as a heating element, a form in which the heating element is installed on the upstream side of the catalyst, and the generated heat is transmitted to the catalyst, and the like can be mentioned. In the control device for an internal combustion engine according to the present invention, the determination means suppresses the occurrence of cracks in the heating element in the electrically heated catalyst via the exhaust gas discharged from the internal combustion engine and flowing into the electrically heated catalyst. An amount of suppression of energy input to the electrically heated catalyst (hereinafter referred to as “input energy”) is determined. Specifically, in the electrically heated catalyst, if the temperature difference in the heating element related to the heating element becomes too large, cracks may be generated in the heating element. An amount of suppression of input energy through the exhaust from the internal combustion engine is determined by the determining means so as to be within the temperature range. The suppression of the input energy according to the present invention is compared with the input energy when the exhaust from the internal combustion engine is exhausted depending on the operating state of the internal combustion engine when crack suppression in the heating element is not considered. And keep it low.

Also, the temperature difference between the heat generating bodies is defined as the temperature difference between the parts in the heat generating body where cracks are likely to occur depending on the size and shape of the electrically heated catalyst provided in the exhaust passage. Generally, since the outer surface of the heating element is a heat dissipation surface to the outside, it tends to be at a lower temperature than the inside of the heating element, and therefore, due to the temperature difference between the outer surface of the heating element and the inside, There are cases where cracks are likely to occur in the heating element. In such a case, the temperature difference between the outer surface of the heating element and the inside thereof can be defined as the temperature difference in the heating element. And in order to implement | achieve the suppression amount of the input energy determined by the determination means, a control means controls the driving | running state of an internal combustion engine. Thereby, the energy of the exhaust gas from the internal combustion engine, that is, the energy of the exhaust gas flowing into the electrically heated catalyst reflects the suppression amount, and as a result, the temperature increase of the electrically heated catalyst due to the exhaust gas is alleviated. Thereby, it is possible to avoid excessively widening of the temperature difference in the heat generating body between the predetermined portions that are likely to cause a temperature difference and cause a crack.

In particular, when the internal combustion engine is cold started, the electric heating catalyst itself is in a relatively low temperature state, and thus there is a tendency that a temperature difference is likely to occur between predetermined parts of the heating element. By suppressing the input energy to the electrically heated catalyst, it is possible to suppress the expansion of the temperature difference in the heat generating body at the time of cold start, thereby avoiding the generation of cracks in the heat generating body. The prior art increases the input energy in order to activate the electrically heated catalyst when the internal combustion engine is cold-started, but the present invention differs from the prior art in that it controls the operating state of the internal combustion engine. Therefore, the input energy via the exhaust is suppressed.

Here, in the control apparatus for an internal combustion engine, the determination means includes the electric heating for causing the temperature difference within the heating element to fall within the predetermined temperature range based on an elapsed time from a cold start of the internal combustion engine. An upper limit integrated value, which is an upper limit value of an integrated value of a predetermined parameter related to the exhaust amount flowing through the catalyst, is calculated as an amount of suppression of the input energy, and the control means is provided from a cold start of the internal combustion engine. The engine output of the internal combustion engine may be controlled so that the actual integrated value of the predetermined parameter does not exceed or approaches the upper limit integrated value calculated by the determining means. Good.

That is, in the above invention, the input energy input to the electrically heated catalyst through the exhaust is grasped through an integrated value from the cold start of a predetermined parameter related to the exhaust amount flowing through the electrically heated catalyst. is there. It is reasonably considered that the input energy to the electrically heated catalyst increases as the integrated value of the displacement increases. Therefore, the input energy to the electrically heated catalyst at the cold start can be grasped through a predetermined parameter related to the exhaust amount, for example, an integrated value of parameters such as the intake amount in the internal combustion engine and the exhaust amount itself. Then, the determining means calculates the upper limit integrated value of the predetermined parameter, and the control means compares the actual integrated value with the upper limit integrated value so that the temperature difference within the heat generating body falls within the predetermined temperature range. The engine output of the internal combustion engine is controlled so that the actual integrated value does not exceed the upper limit integrated value or approaches the upper limit integrated value. Thereby, it is possible to avoid the occurrence of cracks in the heating element during the cold start. The engine output of the internal combustion engine can be controlled via the intake air amount and the like.

Further, as another method of controlling the operation state of the internal combustion engine by the control means, a mode of controlling the exhaust air / fuel ratio of the internal combustion engine can be adopted. Specifically, in the control device for an internal combustion engine, the determination unit is configured to allow the temperature difference within the heating element to fall within the predetermined temperature range based on an elapsed time from a cold start of the internal combustion engine. An upper limit integrated value, which is an upper limit value of an integrated value of a predetermined parameter related to the exhaust amount flowing through the electrically heated catalyst, is calculated as an amount of suppression of the input energy, and the control means is configured to start from a cold start of the internal combustion engine. The exhaust air-fuel ratio by fuel combustion in the internal combustion engine is adjusted so that the actual integrated value of the predetermined parameter does not exceed or approaches the upper limit integrated value calculated by the determining means Then, the exhaust gas temperature may be controlled.

That is, in the above invention, the input energy input to the electrically heated catalyst through the exhaust gas is grasped through an integrated value from a cold start of a predetermined parameter, and the exhaust air-fuel ratio by fuel combustion in the internal combustion engine is set. Based on this, the input energy by the exhaust gas that actually flows into the electrically heated catalyst is controlled. In an internal combustion engine, some relationship can be found between the exhaust air-fuel ratio due to fuel combustion and the exhaust temperature. Therefore, in the present invention, it is possible to control the input energy to the electrically heated catalyst by adjusting the exhaust air-fuel ratio and controlling the exhaust temperature. As a result, the heat generating body at the cold start of the internal combustion engine can be controlled. The expansion of the temperature difference can be suppressed and the occurrence of cracks can be avoided.

For example, when the internal combustion engine is a spark ignition type internal combustion engine, the control means increases the exhaust air-fuel ratio so that the exhaust air-fuel ratio becomes richer as the actual integrated value of the predetermined parameter increases. The exhaust gas temperature may be lowered by adjusting the combustion conditions in In the case of a spark ignition type internal combustion engine, generally, when the exhaust air-fuel ratio is close to the stoichiometry, the exhaust temperature becomes high, and the exhaust temperature decreases as the exhaust air-fuel ratio moves to the rich side. Therefore, as the actual integrated value of the predetermined parameter increases, the combustion condition is adjusted so that the exhaust air-fuel ratio becomes a richer air-fuel ratio as the difference between the actual integrated value and the upper limit integrated value increases. As a result, the exhaust gas temperature can be lowered, and the energy input to the electrically heated catalyst can be suppressed.

Here, in the control device for an internal combustion engine up to the above, in the case where it further comprises estimation means for estimating or detecting the temperature of the electrically heated catalyst, the determination means is estimated or detected by the estimation means. As the temperature of the electrically heated catalyst becomes higher, the amount of energy that is input through the exhaust to the electrically heated catalyst may be reduced. The present applicant has found that the temperature difference between predetermined portions of the heating element tends to decrease as the temperature of the electrically heated catalyst increases. And, as the temperature difference becomes smaller, the possibility that cracks will occur in the heat generating body becomes lower, and even if the amount of suppression of the input energy through the exhaust is made smaller as the temperature of the electrically heated catalyst becomes higher, Generation of cracks can be easily avoided. As a result, the degree of control of the operating state of the internal combustion engine by the control means is relaxed, and it is possible to realize an output close to the original engine output and an exhaust air-fuel ratio state that should be originally intended.

Here, immediately after the cold start of the internal combustion engine, as described above, if the exhaust gas having a relatively high input energy flows into the electrically heated catalyst, the temperature difference in the heat generating body may be increased, and cracks are caused thereby. Can occur. An example of a case where exhaust having relatively high input energy is discharged is during acceleration immediately after a cold start. Therefore, in the control apparatus for an internal combustion engine described above, the control of the operation state of the internal combustion engine according to the amount of suppression of the input energy by the control means is performed in a predetermined acceleration period immediately after the cold start of the internal combustion engine. You may be made to be. By doing so, the control of the operation state of the internal combustion engine by the control means is performed for a limited period, and the deviation from the operation state of the internal combustion engine that should be performed can be suppressed as much as possible.

Also, the control device for an internal combustion engine up to the above can be applied to an internal combustion engine mounted on a hybrid vehicle. In that case, the amount of energy to be charged into the electrically heated catalyst may be adjusted based on an event specific to the hybrid vehicle. Specifically, in the control device for an internal combustion engine described above, the internal combustion engine is mounted on a hybrid vehicle that uses the internal combustion engine and a motor driven by power supplied from a power source as power sources. The determination means may increase the amount of suppression of the input energy to the electrically heated catalyst as the vehicle speed of the hybrid vehicle at the cold start of the internal combustion engine increases.

Generally, in a hybrid vehicle equipped with an internal combustion engine and a motor as drive sources, the drive with only the motor and the drive with the motor and the internal combustion engine are appropriately switched depending on the situation such as the drive load and the power supply capability of the power source. Therefore, there may be a situation where the engine itself is stopped while the vehicle itself is running, and therefore the vehicle speed of the hybrid vehicle is relatively high when the internal combustion engine is cold started. There is also a possibility. In particular, a hybrid vehicle of a type called PHV (plug-in hybrid) has a configuration in which a region in which only a motor can travel is set wider than that of a general hybrid vehicle. The trend of speeding up becomes stronger. When a cold start of the internal combustion engine is performed with the vehicle speed of the hybrid vehicle being high, a relatively large amount of intake air is supplied to the internal combustion engine simultaneously with the cold start, resulting in a large amount of input energy to the electrically heated catalyst. As a result, cracks are easily induced. Therefore, as described above, the higher the vehicle speed of the hybrid vehicle at the time of cold start of the internal combustion engine, the more the amount of suppression of the input energy to the electrically heated catalyst is increased, that is, the input energy is further suppressed. In addition, it is possible to avoid an increase in temperature difference in the heating element.

Here, it is possible to grasp the present invention from another aspect. Specifically, the present invention relates to a control device for an internal combustion engine mounted on a hybrid vehicle that uses an internal combustion engine and a motor driven by electric power supplied from a power source as a power source. An electric heating type catalyst that heats a catalyst having an exhaust purification capability by heat from a heating element that generates heat when supplied with electric power; and the hybrid vehicle includes a power source for the motor while the internal combustion engine is stopped. And a pre-starting heating means for supplying electric power to the electrically heated catalyst and generating heat before starting the internal combustion engine. Further, the pre-starting heat generating means has a temperature difference in the heating element within a predetermined temperature range that is a temperature difference between predetermined portions of the heating element of the electric heating catalyst even if the internal combustion engine is cold started. Power is supplied to the electrically heated catalyst based on the vehicle speed of the hybrid vehicle so that the temperature of the electrically heated catalyst is raised.

The above invention relates to a control device for an internal combustion engine mounted on a hybrid vehicle. As described above, as a feature at the time of cold start of the internal combustion engine in the hybrid vehicle, a relatively large amount of intake air is supplied to the internal combustion engine together with the cold start, and as a result, a large amount of exhaust gas flows into the electrically heated catalyst. The situation can be mentioned. As described above, when a large amount of exhaust gas flows into the electrically heated catalyst during the cold start, as a result, the input energy to the electrically heated catalyst increases, which may increase the temperature difference in the heating element. Therefore, in the above invention, when the internal combustion engine is cold-started from the state in which the internal combustion engine is stopped and the vehicle is driven by the motor, the electrically heated catalyst is generated by the pre-starting heating means based on the vehicle speed at that time. The temperature is raised. If the temperature of the electrically heated catalyst rises, even if the exhaust flows, the temperature difference in the heat generating body is difficult to increase as described above, and therefore, depending on the vehicle speed when the internal combustion engine is cold started, In other words, the electric heating type catalyst is heated prior to the actual cold start in accordance with the intake amount (or exhaust amount) related to the vehicle speed, thereby preventing the temperature difference in the heating element from expanding. is there. Therefore, the present invention avoids the expansion of the temperature difference in the heat generating body by supplying power to the electric heating catalyst while taking into consideration the input energy through the exhaust to the electric heating catalyst.

Further, in the control device for an internal combustion engine, the pre-starting heat generating means may supply power so that the temperature of the electrically heated catalyst increases as the vehicle speed of the hybrid vehicle increases. By doing so, it is possible to prevent an increase in the temperature difference within the heat generating body based on the energy input through the exhaust to the electrically heated catalyst.

In an internal combustion engine equipped with an electrically heated catalyst, the internal combustion engine is controlled appropriately so that the temperature difference that causes cracks does not occur in the heating element that generates heat when energized in the electrically heated catalyst. Providing equipment.

1 is a diagram showing a schematic configuration of a hybrid vehicle including a control device for an internal combustion engine according to an embodiment of the present invention and using the internal combustion engine and a motor as power sources. FIG. 2 is a first cross-sectional view showing a configuration of an electrically heated catalyst for purifying exhaust gas of an internal combustion engine mounted on the hybrid vehicle shown in FIG. 1. FIG. 3 is a second cross-sectional view showing the configuration of an electrically heated catalyst for purifying exhaust gas of an internal combustion engine mounted on the hybrid vehicle shown in FIG. 1. It is a figure which shows the temperature transition of each site | part in the support | carrier in the electrically heated catalyst shown to FIG. 2, FIG. It is a 1st flowchart regarding the control for suppressing the expansion of the temperature difference in the support | carrier of an electrically heated catalyst performed by the control apparatus of the internal combustion engine which concerns on the Example of this invention. It is a figure which shows the correlation with the elapsed time from the cold start for calculating the integrated Ga upper limit in the control flow shown in FIG. 5, and the temperature of an electrically heated catalyst. FIG. 6 is a diagram showing a correlation between an engine speed and an integrated Ga upper limit for calculating a throttle opening upper limit in the control flow shown in FIG. 5. It is a figure which shows transition of integrating | accumulating Ga from a cold start, and Ga when the control flow shown in FIG. 5 is performed. FIG. 6 is a first diagram showing the temperature transition of each part of the electrically heated catalyst and the transition of the temperature difference in the carrier when the control flow shown in FIG. 5 is performed. FIG. 6 is a second diagram showing the temperature transition of each part of the electrically heated catalyst and the transition of the temperature difference in the carrier when the control flow shown in FIG. 5 is performed. It is a 2nd flowchart regarding the control for suppressing the expansion of the temperature difference in the support | carrier of an electrically heated catalyst performed by the control apparatus of the internal combustion engine which concerns on the Example of this invention. FIG. 11 is a first diagram showing the correlation between the engine speed and the temperature of the electrically heated catalyst for determining the exhaust air-fuel ratio in the control flow shown in FIG. 10. FIG. 11 is a second diagram showing the correlation between the engine speed and the temperature of the electrically heated catalyst for determining the exhaust air-fuel ratio in the control flow shown in FIG. 10. FIG. 11 is a third diagram showing the correlation between the engine speed and the temperature of the electrically heated catalyst for determining the exhaust air-fuel ratio in the control flow shown in FIG. 10. It is a figure which shows transition of the integrating | accumulating Ga from a cold start, and an exhaust air fuel ratio when the control flow shown in FIG. 10 is performed. It is a figure which shows transition of the temperature transition of each site | part of an electrically heated catalyst, and transition of the temperature difference in a support | carrier when the control flow shown in FIG. 10 is performed. It is a figure which shows the temperature transition of each site | part of an electrically heated catalyst when the control flow shown in FIG. 10 is performed. It is a figure which shows transition of the temperature difference in a support | carrier for every temperature of an electrically heated catalyst when the control flow shown in FIG. 10 is performed. It is a 3rd flowchart regarding the control for suppressing the expansion of the temperature difference in the support | carrier of an electrically heated catalyst performed by the control apparatus of the internal combustion engine which concerns on the Example of this invention. It is a figure which shows the correlation with an engine speed for determining the throttle opening upper limit in the control flow shown in FIG. 10, an integrated Ga upper limit, and a vehicle speed. It is a 4th flowchart regarding the control for suppressing the expansion of the temperature difference in the support | carrier of an electrically heated catalyst performed by the control apparatus of the internal combustion engine which concerns on the Example of this invention. It is a figure which shows the correlation with the engine speed for determining an exhaust air fuel ratio in the control flow shown in FIG. 18, the temperature of an electrically heated catalyst, and a vehicle speed. It is a 5th flowchart regarding the control for suppressing the expansion of the temperature difference in the support | carrier of an electrically heated catalyst performed by the control apparatus of the internal combustion engine which concerns on the Example of this invention. It is a figure which shows the correlation with the vehicle speed for determining target EHC temperature in the control flow shown in FIG.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Schematic configuration of hybrid system>
FIG. 1 shows a hybrid vehicle 100 including a hybrid system having an internal combustion engine having a control device according to an embodiment of the present invention and two motor generators (hereinafter simply referred to as “motors”) as separate drive sources. It is a figure which shows schematic structure of these. The hybrid vehicle 100 includes the internal combustion engine 10 as a main power source, and includes a motor 21a and a motor 21b as auxiliary power sources.

First, the hybrid system will be described. The crankshaft of the internal combustion engine 10 is connected to the output shaft 23, and the output shaft 23 is connected to the power split mechanism 22. The power split mechanism 22 is connected to the motor 21 a via the power transmission shaft 24 and is also connected to the motor 21 b via the power transmission shaft 25. Here, the power split mechanism 22 switches the transmission of the output of the internal combustion engine and the auxiliary power source and the like by the planetary gear mechanism. A reduction gear 26 is connected to the power transmission shaft 25 connected to the motor 21 b, and drive wheels 28 are connected to the reduction gear 26 via a drive shaft 27. The speed reducer 26 is configured by combining a plurality of gears, reduces the rotational speed of the power transmission shaft 25, and transmits the output from the internal combustion engine 10, the motor 21 a, and the motor 21 b to the drive shaft 27.

Here, the

motors

21 a and 21 b are electrically connected to a PCU (Power Control Unit) 29 including an inverter (not shown), and the PCU 29 is further electrically connected to the battery 30. The PCU 29 converts the DC power extracted from the battery 30 into AC power and supplies the AC power to the

motors

21 a and 21 b, and converts the AC power generated by the

motors

21 a and 21 b into DC power and supplies it to the battery 30. It is the electric power control unit comprised by these. More specifically, the

motors

21a and 21b are constituted by AC synchronous motors. When an excitation current is applied, the

motors

21a and 21b generate torque, and when torque is applied from the outside, for example, the power split mechanism 22 is driven from the internal combustion engine 10. When kinetic energy is input via the power, electric power is generated by converting the kinetic energy into electrical energy. The generated electric power is supplied to the battery 30 via the PCU 29. The motor 21b acts as a generator when the vehicle is decelerated, and converts so-called regenerative power generation from kinetic energy transmitted from the drive wheels 28 to the power transmission shaft 25 via the drive shaft 27 and the speed reducer 26 into electric energy. The electric power generated thereby is also supplied to the battery 30 via the PCU 29. A hybrid vehicle 100 shown in FIG. 1 is a so-called plug-in hybrid vehicle, and is provided with a charging plug 31 so that electric power can be supplied from an external power source 32.

1 is a spark ignition internal combustion engine having a fuel injection valve (not shown) for injecting fuel into a combustion chamber and an ignition plug (not shown). The intake passage 12 of the internal combustion engine 1 is provided with an air flow meter 13 for detecting the intake flow rate of the passage, and a throttle valve 14 for adjusting the intake flow rate of the intake passage 12 is provided downstream thereof. The exhaust passage 2 of the internal combustion engine 1 is provided with an EHC (electrically heated catalyst) 1 for purifying exhaust gas. The EHC 1 is a device that raises the temperature of a catalyst supported on a carrier by energizing an electrode laid on the carrier, and a specific configuration thereof will be described later.

The hybrid vehicle 100 having the hybrid system configured as described above is an electronic control unit for controlling the fuel injection in the internal combustion engine 10 and the PCU 29 that controls power transfer between the

motors

21a and 21b and the battery 30. An ECU 20 is provided. Specifically, the crank position sensor 11 and the accelerator opening sensor 15 are electrically connected to the ECU 20, and the operation state of the internal combustion engine 10 is grasped by passing each detection value. Further, the ECU 20 is also electrically connected to a water temperature sensor 16 that detects the coolant temperature of the internal combustion engine 10, the air flow meter 13, and the throttle valve 14. The ECU 20 also monitors the amount of power stored in the battery 30 via the PCU 29. For example, when the ECU 20 determines that the amount of power stored in the battery 30 is decreasing, power is generated by transmitting the engine output of the internal combustion engine 1 to the motor 21 a, and the electricity generated by the motor 21 a is generated via the PCU 29. Is stored. The ECU 20 is also electrically connected to the temperature sensor 6a and the air-fuel ratio sensor 6b shown in FIG. 2, and is further electrically connected so that energization to the EHC 1 can be controlled.

<Schematic configuration of EHC>
Here, a specific configuration of the EHC 1 will be described with reference to FIGS. 2 and 3. FIG. 2 is a cross-sectional view of the EHC 1 along the exhaust flow direction, and the white arrows in FIG. 2 indicate the exhaust flow direction in the exhaust passage 2. FIG. 3 is a cross-sectional view taken along the line BB shown in FIG. The EHC 1 includes a catalyst carrier 3, a case 4, a mat 5, and an electrode 7. The catalyst carrier 3 is accommodated in the case 4. The catalyst carrier 3 is formed in a cylindrical shape, and is installed so that its central axis is coaxial with the central axis A of the exhaust passage 2. The central axis A is a central axis common to the exhaust passage 2, the catalyst carrier 3, and the case 4. A three-way catalyst 13 is supported on the catalyst carrier 3. The catalyst supported on the catalyst carrier 3 is not limited to a three-way catalyst, and may be an oxidation catalyst, an occlusion reduction type NOx catalyst, or a selective reduction type NOx catalyst. It can be selected as appropriate.

The catalyst carrier 3 is formed of a material that generates electric resistance when heated. An example of the material of the catalyst carrier 3 is SiC. The catalyst carrier 3 has a plurality of passages extending in the direction in which the exhaust flows (that is, in the direction of the central axis A) and having a cross section perpendicular to the direction in which the exhaust flows in a honeycomb shape. Exhaust gas flows through this passage. The cross-sectional shape of the catalyst carrier 3 in the direction orthogonal to the central axis A may be an ellipse or the like.

A pair of electrodes 7 are connected to the outer peripheral surface of the catalyst carrier 3. The electrode 7 is formed by a surface electrode 7a and a shaft electrode 7b. The surface electrode 7 a extends along the outer circumferential surface of the catalyst carrier 3 in the circumferential direction and the axial direction, that is, so as to cover the outer circumferential surface of the catalyst carrier 3. The surface electrodes 7 a are provided on the outer peripheral surface of the catalyst carrier 3 so as to face each other with the catalyst carrier 3 interposed therebetween. One end of the shaft electrode 7b is connected to the surface electrode 7a. The other end of the shaft electrode 7 b protrudes outside the case 4 through the electrode chamber 9 formed in the case 4. Electric power is supplied from the battery 30 to the electrode 7 configured as described above, and the catalyst carrier 3 is energized. When the catalyst carrier 3 generates heat due to this energization, the three-way catalyst 13 supported on the catalyst carrier 3 is heated and its activation is promoted. In this way, the power supply for activating the catalyst in the EHC 1 via the electrode 7 is controlled by the ECU 20.

Here, the case 4 is made of metal. As a material for forming the case 4, a stainless steel material can be exemplified. A mat 5 is sandwiched between the inner wall surface of the case 4 and the outer peripheral surface of the catalyst carrier 3. That is, the catalyst carrier 3 is supported by the mat 5 in the case 4. The mat 5 is made of an electrical insulating material. Examples of the material for forming the mat 5 include ceramic fibers mainly composed of alumina. As described above, since the mat 5 is sandwiched between the catalyst carrier 3 and the case 4, electricity is prevented from leaking to the case 4 when the catalyst carrier 3 is energized. The mat 5 is divided into an upstream portion 5a and a downstream portion 5b, and a space is formed between the upstream portion 5a and the downstream portion 5b. An electrode chamber 9 for passing the axial electrode 7b is defined. The mat 5 may be divided into an upstream portion 5a and a downstream portion 5b, and a space serving as an electrode chamber may be defined by forming a through hole only in a portion through which the electrode 7 of the mat 5 passes.

Also, an electrode support member 8 that supports the shaft electrode 7b is provided in a through-hole that is opened in the case 4 so as to pass the shaft electrode 7b. The electrode support member 8 is formed of an electrical insulating material, and insulation between the case 4 and the shaft electrode 7b is maintained.

In this embodiment, the catalyst carrier 3 corresponds to the heating element according to the present invention. However, the heating element according to the present invention is not limited to the carrier supporting the catalyst. For example, the heating element may be a structure installed on the upstream side of the catalyst. In this case, the heat generated by the heating element is the catalyst. As a result, the catalyst is heated.

<EHC heat distribution and output suppression control during cold start>
FIG. 4 is a diagram for schematically explaining the transition of the temperature of the catalyst carrier 3 of the EHC 1 when the internal combustion engine 10 is cold started. FIG. 4A is a cross-sectional view when the EHC 1 is cut in a direction orthogonal to the central axis. In FIG. 4A, the electrode 7 is omitted for convenience. FIG. 4B is a diagram showing the temperature transition of each part of the catalyst carrier 3 when the internal combustion engine 10 is cold-started. In FIG. 4B, the horizontal axis represents time, the vertical axis represents the temperature of the catalyst carrier 3, and the alternate long and short dash line represents the temperature of the side wall surface of the catalyst carrier 3 (the surface in contact with the mat 5). The broken line represents the temperature transition in the vicinity of the side wall inside the catalyst carrier 3 (for example, a portion entering about 5 mm inward from the side wall surface), and the solid line represents the temperature transition in the center of the catalyst carrier 3. Yes. FIG. 4C shows a change in temperature difference ΔT between the side wall surface of the catalyst carrier 3 and the vicinity of the side wall inside the catalyst carrier 3 during cold start of the internal combustion engine 10 (hereinafter, referred to as “temperature difference in the carrier”). FIG.

When the temperature of the catalyst carrier 3 is increased by exhaust, the side wall surface of the catalyst carrier 3 has a large amount of heat released to the mat 5, and therefore, the temperature hardly rises compared to the inside. Therefore, as shown in FIG. 4, when the energy input to the catalyst carrier 3 is rapidly increased by exhaust from the internal combustion engine 10 during the cold start of the internal combustion engine 10, the temperature between the side wall surface and the inside of the catalyst carrier 3 is increased. There is a difference. In particular, the temperature difference ΔT between the side wall surface of the catalyst carrier 3 and the vicinity of the side wall tends to increase. And when the temperature difference (DELTA) T between the side wall surface in such a catalyst carrier 3 and a side wall vicinity part expands too much, there exists a possibility that a crack may arise in the catalyst carrier 3. FIG.

In EHC1, if a crack occurs in the catalyst carrier 3, the electrical resistance value of the cracked portion becomes higher than that of the other portions. Therefore, when the EHC 1 is energized, the distribution of the energization amount in the catalyst carrier 3 becomes non-uniform, a larger temperature difference occurs in the catalyst carrier 3, and there is a risk of further increase / increase of cracks. But it must be avoided.

In view of this, it is preferable to perform control for suppressing the generation of cracks in the catalyst carrier 3 during the cold start of the internal combustion engine 10 which is particularly prone to cracks. A specific embodiment of the control will be described with reference to FIG. To do. FIG. 5 is a flowchart of the output suppression control performed by the ECU 20, and the control is repeatedly executed by the ECU 20 every predetermined time. The ECU 20 substantially corresponds to a computer including a CPU, a memory, and the like, and the control according to the flowchart shown in FIG. 5 and various controls described later are executed by executing a control program there.

First, in S101, based on the detected value by the accelerator opening sensor 15, it is determined whether or not the accelerator opening in the vehicle 100 is larger than a predetermined opening A0 as a reference. The predetermined opening A0 is a threshold value for determining whether or not there is a rapid acceleration request for the internal combustion engine 10 included in the hybrid system. If an affirmative determination is made in S101, the process proceeds to S102, and if a negative determination is made, this control is terminated.

Next, in S102, it is determined whether or not a cold start request has been issued to the internal combustion engine 10. Generally, the cold start of the internal combustion engine is an engine start when the temperature of the internal combustion engine is relatively low. However, in the internal combustion engine 10 included in the hybrid system, the vehicle 100 travels with only the driving force of the

motors

21a and 21b according to the travel request of the driver, and the drive of the internal combustion engine 1 together with both motors. Since “HV traveling” that travels by force is switched as appropriate, cold start in the internal combustion engine 10 is engine start when the entire hybrid system is stopped, and the traveling state of the vehicle 100 is from EV traveling to HV traveling. Includes engine start when switched. Whether or not the engine start of the internal combustion engine 10 is a cold start is based on the coolant temperature by the water temperature sensor 16, the time that the internal combustion engine 10 has been stopped (ie, the soak time of the internal combustion engine 10), or the like. It is judged. If a positive determination is made in S102, the process proceeds to S103, and if a negative determination is made, the present control is terminated.

Next, the case where the process proceeds to S103 will be described. If both affirmative determination is made in S101 and S102, the process proceeds to S103. At this time, the internal combustion engine 10 is subjected to a relatively large acceleration request in the cold start, and as a result, the energy input to the catalyst carrier 3 of the EHC 1 can rapidly increase (hereinafter referred to as “cold start acceleration state”). Will be placed in. When the input energy to the catalyst carrier 3 is suddenly increased, the temperature difference in the carrier, which causes the generation of cracks, is easily increased as described with reference to FIG. Therefore, the processing after S103 is performed in order to suppress the occurrence of cracks in the catalyst carrier 3.

In S103, the temperature of the catalyst carrier 3 of the EHC 1 (hereinafter referred to as “EHC temperature”) Tehc is calculated based on the detection value of the temperature sensor 6a, and the EHC temperature Tehc and the internal combustion engine 10 are cold-started. On the basis of the elapsed time since then, the upper limit value (hereinafter referred to as “integrated intake air amount upper limit”) of the integrated value of the intake air amount (hereinafter referred to as “integrated intake air amount”) in the cold start acceleration state of the internal combustion engine ) Is calculated. The upper limit of the integrated intake air amount is a limit value related to the integrated intake air amount that is set in order to suppress rapid energy input to the catalyst carrier 3. Therefore, the integrated intake air amount upper limit corresponds to the “suppression amount of input energy via exhaust” in the present invention, and the processing according to S103 corresponds to processing by the determining means according to the present invention.

Here, an example of calculating the integrated intake air amount upper limit gasummax will be described with reference to FIG. FIG. 6 is a map in which the horizontal axis represents the elapsed time since the cold start, and the vertical axis represents the integrated intake air amount upper limit gasummax. By following this map, the integrated intake air amount upper limit gasummax can be calculated based on the elapsed time from the cold start. In the map, as shown in FIG. 6, as the elapsed time becomes shorter, the integrated intake air amount upper limit gasummax also decreases, and the increase rate of the integrated intake air amount upper limit tends to increase with time. Further, the present applicant has found that the catalyst carrier 3 tends to generate a larger temperature difference ΔT within the carrier if its EHC temperature is low. Therefore, the relative relationship between the elapsed time and the cumulative intake air amount upper limit gasummax is set so that the value of the cumulative intake air amount upper limit gasummax with respect to the elapsed time becomes smaller as the bed temperature Tehc itself of the catalyst carrier 3 is lower. ing. As described above, the integrated intake air amount upper limit gasummax is calculated based on both the elapsed time from the cold start and the EHC temperature Tehc, so that energy input is performed based on the thermal state of the catalyst carrier 3 accurately. Can be realized.

Further, after an affirmative determination is made in S102, S104 is performed in parallel with the process S103. In S104, the actual intake air amount Ga from the cold start of the internal combustion engine 10 is integrated, and the integrated intake air amount gasum is calculated. Specifically, a process for integrating the detection values of the air flow meter 13 is performed. After the processes of S103 and S104 are performed, the determination process of S105 is performed. In S105, it is determined whether or not the integrated intake air amount gasum calculated in S104 is larger than the integrated intake air amount upper limit gasummax calculated in S103. An affirmative determination in S105 means that excessive energy is input to the catalyst carrier 3 at the time of cold start, and the temperature difference ΔT in the carrier may be increased. Therefore, if an affirmative determination is made in S105, the processing after S106 is performed in order to suppress the excessive energy input. On the other hand, if a negative determination is made in S105, it is considered that the temperature difference ΔT in the carrier does not increase to the extent that there is a concern about the occurrence of cracks. Therefore, the processing after S106 is not performed, and this control is terminated.

Next, in S106, based on the detected value of the accelerator opening sensor 15, the target opening (hereinafter referred to as the following) of the throttle valve 14 for satisfying the intake amount necessary for realizing the acceleration request according to the accelerator opening. Tatag) (referred to as “target throttle opening”) is calculated. Specifically, based on the relative relationship between the detected accelerator opening, the engine speed of the internal combustion engine 10, and the output torque of the

motors

21a and 21b, the target throttle is determined from the control map stored in the ECU 20. An opening degree tagag is calculated. When the process of S106 ends, the process proceeds to S107.

In S107, the opening (hereinafter referred to as “throttle opening upper limit”) tamax of the throttle valve 14 to be taken in order to realize the integrated intake air amount upper limit gasummax calculated in S103 is determined. The throttle opening upper limit tamax is a limit value related to the opening of the throttle valve 14 that realizes an intake air amount for preventing the in-carrier temperature difference ΔT of the catalyst carrier 3 from being excessively increased. The determination of the throttle opening upper limit tamax will be described with reference to FIG. FIG. 7 is a map in which the horizontal axis is the engine rotation speed and the vertical axis is the throttle opening upper limit tamax. By following this map, the throttle opening upper limit tamax can be calculated based on the engine speed. As a general characteristic of the internal combustion engine 10, the opening degree of the throttle valve 14 increases as the engine speed increases. Further, as described above, the lower the bed temperature Tehc of the catalyst carrier 3, the larger the temperature difference ΔT in the carrier in the catalyst carrier 3 tends to increase. Therefore, it is preferable to keep the energy input to the EHC 1 lower. Therefore, as shown in FIG. 6, the throttle opening upper limit tamax is calculated as shown in FIG. 7 in view of the fact that the value of the integrated intake air amount upper limit gasummax is calculated as the EHC temperature Tehc decreases. The relative relationship between the engine rotation speed and the throttle opening upper limit tamax is set so that the value of the throttle opening upper limit tamax with respect to the engine rotation speed decreases as the value of the integrated intake amount upper limit gasummax decreases. Thus, the throttle opening upper limit tamax is determined based on both the engine speed and the integrated intake air amount upper limit gasummax reflecting the EHC temperature Tehc, so that the thermal state of the catalyst carrier 3 can be accurately taken into account. In addition, intake air amount control for energy input can be realized. When the process of S107 ends, the process proceeds to S108.

In S108, it is determined whether or not the target throttle opening degree tagag is larger than the throttle opening upper limit tamax. In other words, if the intake amount increases, the exhaust amount flowing into the EHC 1 increases, and as a result, the energy input to the EHC 1 increases. As a result, the determination process in S108 determines the requested operating state of the internal combustion engine 10. It is determined whether or not the intake air amount to be realized is an intake air amount that can increase the temperature difference ΔT in the carrier. Therefore, if an affirmative determination is made in S108, it can be reasonably determined that the temperature difference ΔT in the carrier can be increased, and the routine proceeds to S109, where the value of the target throttle opening degree tag is limited to the throttle opening upper limit tamax. On the other hand, if a negative determination is made in S108, no restriction on the target throttle opening degree tag is performed.

Then, after the processing of S108 and S109, in S110, the opening degree of the throttle valve 14 is controlled according to the target throttle opening degree tagag. As a result, when the target throttle opening degree tag is restricted in S109, the target throttle opening degree tag is restricted in S109 so that the opening degree of the throttle valve 14 becomes the restriction opening degree. If not, the opening degree of the throttle valve 14 is controlled to be the value calculated in S106. When the process of S110 ends, the process proceeds to S111.

In S111, it is determined whether or not a predetermined time has elapsed since the internal combustion engine 10 started cold start. This predetermined time is defined as a time until the EHC temperature Tehc rises to some extent and reaches a state in which no crack is generated due to the temperature difference ΔT in the carrier. Therefore, if an affirmative determination is made in S111, the present control is terminated because the possibility of cracking in the catalyst carrier 3 is low, and if a negative determination is made, there is still a possibility that the EHC 1 may crack. The processes after S103 are repeated. In S111, the continuation of the main control is determined as the predetermined time elapses. Alternatively, the continuation of the main control may be determined based on the current EHC temperature Tehc. From the above, the processing of S103 to S111 described above corresponds to the processing by the control means according to the present invention.

Thus, according to the present output suppression control, when the internal combustion engine 10 is cold started, the accumulated intake air amount is excessively increased in the carrier temperature difference ΔT in the catalyst carrier 3 according to various parameters including the EHC temperature Tehc. Control is performed so as not to exceed the limit value for preventing enlargement. As a result, it is possible to suppress the occurrence of cracks in EHC1. In this control, an upper limit value is set for the integrated intake air amount, and the output is suppressed as a result in order to suppress it. However, since this control limits the integrated intake amount immediately after the cold start of the internal combustion engine 10, the situation where the output is not suddenly restricted during the acceleration does not occur. It becomes difficult to let you feel.

Here, the effect of the control device according to the present invention will be described with reference to FIGS. 8, 9A, and 9B. First, FIG. 8A shows the transition of the integrated intake air amount when the output suppression control shown in FIG. 5 is performed, and FIG. 8B illustrates the transition of the intake air amount Ga. In FIG. 8, the transition indicated by the solid line relates to the present output suppression control, and the broken line relates to the related art, that is, relates to the form in which the intake air amount restriction process based on the integrated intake air amount upper limit is not performed. Is. As shown in FIG. 8 (a), in this control, since the upper limit of the integrated intake air amount is set immediately after the start of the cold start acceleration, the rate of increase of the integrated intake air amount at the initial stage of acceleration compared to the case where there is no such setting. Is low. Thereafter, by terminating the present control by the determination in S111, the setting of the integrated intake air amount upper limit is canceled, so that the increase rate of the integrated intake air amount becomes approximately the same as the case where there is no such setting.

FIG. 8B shows the transition of the intake air amount when the restriction of the integrated intake air amount is performed. As can be seen, in this control, the intake air amount Ga is also kept low immediately after the start of the cold start acceleration, compared to the case where the upper limit of the integrated intake air amount is not set. Therefore, as described above, since the intake air amount Ga is not suddenly reduced in order to suppress the expansion of the temperature difference in the carrier, it is possible to avoid a situation in which the output of the internal combustion engine 10 is greatly restricted during acceleration. Therefore, it becomes possible to reduce the deterioration of the dribabil.

Next, in FIG. 9A and FIG. 9B, the temperature transition of the side wall surface of the catalyst carrier 3 and the vicinity of the side wall is illustrated in the upper part of each figure, and the transition of the temperature difference ΔT in the carrier is illustrated in the lower part of each figure. In detail, in both figures, line L1 shows the temperature transition of the side wall surface of catalyst carrier 3 when this output suppression control is performed, and line L2 shows the catalyst carrier when this output suppression control is performed. 3 shows a temperature transition in the vicinity of the side wall, and a temperature difference ΔT in the carrier, which is a temperature difference between the side wall surface and the side wall near the both lines, is indicated by a line L5. Similarly, in both figures, the line L3 indicates the temperature transition of the side wall surface of the catalyst carrier 3 in the prior art, that is, when the output suppression control is not performed, and the line L4 indicates the side wall of the catalyst carrier 3 in the prior art. The temperature transition in the vicinity is shown, and the temperature difference ΔT in the carrier, which is the temperature difference between the side wall surface and the side wall vicinity related to both lines, is indicated by a line L6.

FIG. 9A is a diagram showing the transition of each parameter when the EHC temperature is relatively low at the initial stage of acceleration in the cold start acceleration state of the internal combustion engine 10, and conversely, FIG. 9B shows the EHC at the initial stage of acceleration. It is a figure which shows transition of each parameter when temperature is comparatively high. As can be seen from these figures, by performing this output suppression control, the temperature difference ΔT in the carrier is reduced in the catalyst carrier 3 as compared with the case of the prior art even at a low temperature at which the temperature difference ΔT in the carrier is easy to expand. It can be maintained below ΔT1 (the temperature range below the criterion corresponds to the “predetermined temperature range” in the present invention), which is the threshold value for occurrence of cracks.

Further, as can be understood by comparing the lower stage of FIG. 9A and the lower stage of FIG. 9B, the degree of expansion of the temperature difference ΔT in the carrier decreases as the EHC temperature in the initial stage of acceleration increases. Therefore, the higher the EHC temperature in the early stage of acceleration, the higher the integrated intake air amount upper limit value can be set, and the reduction (suppression amount) in engine output of the internal combustion engine 10 can be reduced. Thus, the correlation between the EHC temperature and the integrated intake air amount upper limit is reflected in the control map shown in FIG. Therefore, according to this output suppression control, even if the crack generation threshold is set to ΔT2 lower than ΔT1, the in-carrier temperature difference ΔT can be maintained below ΔT2 and the output of the internal combustion engine 10 can be suppressed. Can be reduced.

<Modification>
In the above embodiment, the invention for avoiding the occurrence of cracks in the EHC 1 in the internal combustion engine 10 mounted on the hybrid vehicle 100 has been described. However, the present invention is a vehicle driven only by the internal combustion engine 10, that is, The present invention is also applicable to the internal combustion engine 10 in a vehicle that does not use a motor driven by electric power as a power source. Furthermore, even if the internal combustion engine 10 is a compression self-ignition internal combustion engine, the present invention can be applied.

Further, in the output suppression control, when it is determined in S111 that the predetermined time has elapsed, the control is terminated, but in this case, the setting of the integrated intake air amount upper limit is not performed, so that the internal combustion engine 10 exhibits. There is a possibility that the upper limit of the output that can be changed rapidly. Therefore, after the predetermined time has elapsed, the setting of the integrated intake air amount upper limit is not stopped immediately, but the value of the integrated intake air amount upper limit is gradually increased so as to finally reach a state where there is substantially no upper limit. Thus, a sudden change in the output of the internal combustion engine 10 may be avoided. Further, the adjustment for changing the upper limit value of the integrated intake air amount is not necessarily performed after the determination of the elapse of the predetermined time in S111, and the possibility of occurrence of cracks does not increase according to the temperature difference ΔT in the carrier. In the range, the adjustment process may be started at a certain timing after the elapse of the predetermined time. Note that the change in the intake air amount due to the adjustment appears in the change in the intake air amount during the suppression return period in FIG.

A second embodiment of the control device for the internal combustion engine 10 according to the present invention will be described with reference to FIGS. FIG. 10 is a flowchart of the exhaust air-fuel ratio control for suppressing the occurrence of cracks in the EHC 1, and among the processes constituting the control, substantially the same process as the process constituting the output suppression control shown in FIG. Are given the same reference numerals and are not described in detail. Specifically, in the exhaust air-fuel ratio control shown in FIG. 10, the processing of S106 to S110 of the output suppression control shown in FIG. 5 is replaced with S201 and S202. Therefore, if an affirmative determination is made in S105, the processing of S201 and S202 is performed, and the process proceeds to S111.

More specifically, in S201, in order to eliminate excessive input energy to the EHC 1 that may cause cracks in the temperature difference ΔT in the carrier due to the difference between the intake air amount integrated gasum and the integrated intake air amount upper limit gasummax, the internal combustion engine 1 The control amount for shifting the air-fuel ratio of the exhaust gas from the exhaust gas to the rich side (that is, the control amount related to the exhaust air-fuel ratio for bringing the stoichiometric air-fuel ratio to the rich-side air-fuel ratio, ") Is determined. Since the internal combustion engine 10 is a spark ignition type internal combustion engine (gasoline engine), usually, the combustion conditions are controlled so that the exhaust air-fuel ratio becomes an air-fuel ratio in the vicinity of the stoichiometry in order to optimize the combustion efficiency. In this specification, this normal combustion control is referred to as normal stoichiometric control from the viewpoint of the exhaust air-fuel ratio. In this normal stoichiometric control, as a result of optimizing the combustion efficiency, the exhaust temperature basically becomes relatively high, so that the energy of the exhaust flowing into the EHC 1 is also in a high energy state. The present invention pays attention to the fact that the exhaust under normal stoichiometric control has such high energy, and in order to reduce the energy of the exhaust in S201, the exhaust air-fuel ratio is set to the rich side. The combustion condition in the internal combustion engine 10 is adjusted so as to shift to, that is, the rich control amount is determined.

Here, a specific method for determining the rich control amount will be described with reference to FIGS. FIGS. 11 to 13 are control maps that define the correlation between the engine speed and the exhaust air-fuel ratio, with the horizontal axis representing the engine speed of the internal combustion engine 10 and the vertical axis representing the exhaust air-fuel ratio. Further, the correlation is defined for each EHC temperature, and according to this map, the exhaust air for suppressing the input energy to the EHC 1 based on the engine speed of the internal combustion engine 10 and the EHC temperature of the EUC 1. The fuel ratio, that is, the rich control amount can be calculated. As described above, as the EHC temperature becomes higher, the temperature difference ΔT in the carrier becomes harder to increase. Therefore, in these control maps, when the EHC temperature is low, the engine rotational speed is higher than when the EHC temperature is high. The above correlation for each EHC temperature is set so that the phase of the exhaust air-fuel ratio becomes richer, in other words, the rich control amount increases.

In the present embodiment, the rich control amount may be determined according to any control map shown in FIGS. Here, the characteristics of the control map shown in each figure will be described below.
<Control map shown in FIG. 11>
In this control map, the correlation between the engine speed and the exhaust air / fuel ratio is set so that the rich control amount increases as the initial engine speed of the internal combustion engine decreases and the rich control amount decreases as the engine speed increases. Has been. If the rich control amount is determined according to the control map, the exhaust air-fuel ratio is strongly enriched at a low temperature at which the EHC 1 is likely to crack, that is, immediately after the cold start of the internal combustion engine 10, so that the acceleration air-fuel ratio is increased. While suppressing the sum of the rich control amounts in the entire period (the period from the initial acceleration to the end of acceleration), it is possible to avoid the temperature difference in the carrier from being efficiently expanded. On the other hand, since the exhaust air-fuel ratio is always richly enriched at the beginning of acceleration when the engine speed is low, excessive rich control is performed when acceleration is stopped halfway.
<Control map shown in FIG. 12>
In this control map, the correlation between the engine speed and the exhaust air / fuel ratio, which is opposite to the control map shown in FIG. 11, is set. Specifically, the rich control amount is increased in the later stage of acceleration when the engine speed of the internal combustion engine is higher. As the engine speed increases, the rich control amount decreases. Therefore, if the rich control amount is determined according to the control map, it is possible to avoid excessive rich control when the acceleration is stopped in the middle of acceleration, etc., but the sum of the rich control amounts over the entire acceleration period. Tend to increase.
<Control map shown in FIG. 13>
In this control map, a correlation between the engine speed and the exhaust air / fuel ratio, which is positioned between the control map shown in FIG. 11 and the control map shown in FIG. 12, is set. Specifically, the engine speed of the internal combustion engine is set. The rich control amount is constant regardless of the speed, and the rich control amount changes according to the EHC temperature. Therefore, if the rich control amount is determined according to the control map, a tendency regarding the rich control amount between the case of using the control map shown in FIG. 11 and the case of using the control map shown in FIG. 12 is obtained.

As described above, based on the characteristics according to each control map, in S201, the rich control amount can be determined according to any one of the control maps of FIGS. When S201 ends, the process proceeds to S202, and based on the rich control amount determined in S201, the exhaust air-fuel ratio is shifted to the rich side in order to suppress the input energy to EHC1. In this embodiment, the fuel injection amount in the internal combustion engine 10 is adjusted to achieve the target rich exhaust air-fuel ratio. When the process of S202 ends, the process proceeds to S111, and the determination process described above is performed.

When the exhaust air / fuel ratio control is performed in this manner, when the internal combustion engine 10 is cold-started, the actual integrated intake air amount exceeds the integrated intake air amount upper limit according to various parameters including the EHC temperature Tehc. The rich control of the exhaust air-fuel ratio is performed so that the temperature difference ΔT in the carrier at the catalyst carrier 3 does not excessively increase, and as a result, the energy input to the EHC 1 via the exhaust is suppressed. In this control, unlike the output suppression control according to the first embodiment, the input energy to the EHC 1 is suppressed without limiting the intake air amount, and therefore the output of the internal combustion engine 10 is not limited. However, the fuel consumption may increase due to the rich control performed by increasing the fuel injection amount by this control.

Here, the effect of the control device according to the invention will be described with reference to FIGS. 14, 15A, 15B, and 15C. First, FIG. 14A shows the transition of the integrated intake air amount when the exhaust air-fuel ratio control shown in FIG. 10 is performed, and FIG. 14B shows the air-fuel ratio of the exhaust from the internal combustion engine 10, that is, EHC. The transition of the air-fuel ratio of the exhaust gas flowing in is illustrated. The transition of the integrated intake air amount upper limit setting in FIG. 14A relates to the integrated intake air amount upper limit setting gasummax calculated in S103 based on the control map shown in FIG. The present invention relates to the actual intake air amount in the internal combustion engine 10 when WOT acceleration (full throttle acceleration) is performed as an example of acceleration at the time of start-up.

In the example shown in FIG. 14, the actual intake air amount has exceeded the integrated intake air amount upper limit gasummax after t1 has elapsed since the start of WOT acceleration at the time of cold start. The processing of S201 and S202 in the control is performed. The transition of the exhaust air-fuel ratio at this time will be described with reference to FIG. 14B. Immediately after the start of WOT acceleration, the fuel injection amount is temporarily increased to correspond to the start of WOT acceleration. However, after that, the normal stoichiometric control is performed so that the exhaust air-fuel ratio becomes an air-fuel ratio in the vicinity of the stoichiometric. When the time t1 elapses, the exhaust air-fuel ratio is controlled to the rich side by the rich control related to the processing of S201 and S202. This rich control is performed to suppress the input energy to the EHC 1 due to the exhaust as described above. Thereafter, when a predetermined time has elapsed in S111, that is, when the time t2 when it is determined that the possibility of occurrence of cracks is low in EHC1, the exhaust air-fuel ratio control is terminated, and the exhaust air-fuel ratio by the normal stoichiometric control is completed. Transition to control.

Next, the upper stage of FIG. 15A and FIG. 15B illustrate the temperature transition of the side wall surface and the vicinity of the side wall of the catalyst carrier 3, and the lower stage of FIG. 15A illustrates the transition of the temperature difference ΔT in the carrier. Specifically, in both figures, a line L11 indicates a temperature transition of the side wall surface of the catalyst carrier 3 when the exhaust air-fuel ratio control is performed, and a line L12 indicates a time when the exhaust air-fuel ratio control is performed. The temperature transition in the vicinity of the side wall of the catalyst carrier 3 is shown, and the temperature difference ΔT in the carrier, which is the temperature difference between the side wall surface and the side wall near the both lines, is indicated by a line L15 in the lower part of FIG. 15A. . Similarly, in both figures, a line L13 shows the temperature transition of the side wall surface of the catalyst carrier 3 in the prior art when the exhaust air-fuel ratio control is not performed, that is, the line L14 shows the catalyst carrier 3 in the prior art. The temperature transition in the vicinity of the side wall is shown, and the temperature difference ΔT in the carrier, which is the temperature difference between the side wall surface and the side wall near the both lines, is indicated by a line L16 in the lower part of FIG. 15A.

FIG. 15A is a diagram showing the transition of each parameter when the EHC temperature is relatively low at the initial stage of acceleration in the cold start acceleration state of the internal combustion engine 10, and conversely, FIG. 15B shows the EHC at the initial stage of acceleration. It is a figure which shows transition of each parameter when temperature is comparatively high. 15A shows the transition of the temperature difference ΔT in the carrier when the exhaust air-fuel ratio control is performed (that is, the transition represented by the line L15 when the EHC temperature is low), and FIG. Although not shown in FIG. 15, the change in the temperature difference ΔT in the carrier when the exhaust air-fuel ratio control is performed (that is, the line L17 corresponding to the case where the EHC temperature is high) calculated from the temperature change shown in FIG. 15B. FIG. 15C shows a comparison with the transition represented by.

As can be seen from these drawings, the exhaust air / fuel control is performed, so that the temperature difference ΔT in the carrier can be reduced compared to the case of the prior art even at a low temperature at which the temperature difference ΔT in the carrier is easily increased. Can be maintained below ΔT1 (the temperature range below the criterion corresponds to the “predetermined temperature range” in the present invention). Further, as indicated by a line L17 in FIG. 15C, when the EHC temperature in the initial stage of acceleration is increased, the degree of expansion of the in-carrier temperature difference ΔT is reduced. Therefore, the rich control amount determined in S201, that is, the extent of the air-fuel ratio shift from the stoichiometric vicinity to the rich side, may be reduced as the EHC temperature in the early stage of acceleration increases. By doing in this way, the fuel consumption for exhaust enrichment performed for crack suppression can be suppressed.

A third embodiment of the control device for the internal combustion engine 10 according to the present invention will be described with reference to FIGS. FIG. 16 is a flowchart of control for suppressing the occurrence of cracks in the EHC 1 as a modified example of the output suppression control shown in FIG. 5, and among the processes constituting the control, the output suppression control shown in FIG. The same reference numerals are assigned to processes that are substantially the same as the processes that constitute, and the detailed description thereof is omitted. Specifically, the output suppression control illustrated in FIG. 16 is obtained by replacing the process of S107 of the output suppression control illustrated in FIG. 5 with S301.

Therefore, the process of S301 performed after the process of S106 is completed will be described. In S301, the throttle opening upper limit tamax is determined in the same manner as in S107. In this embodiment, in addition to the engine rotational speed of the internal combustion engine 10 and the integrated intake air amount upper limit gasummax, the throttle opening upper limit tamax is determined. The vehicle speed of the hybrid vehicle 100 is considered. Accordingly, a method for determining the throttle opening upper limit tamax in S301 will be described based on FIG. In this embodiment, the throttle opening upper limit tamax is determined using the control map shown in FIG. 17A and the control map shown in FIG. The control map shown in FIG. 17A is substantially the same as the control map shown in FIG. 7 corresponding to the process of S106, and therefore detailed description thereof is omitted. Then, according to the control map shown in FIG. 17A, the correlation between the engine speed and the throttle opening upper limit tamax is selected based on the integrated intake amount upper limit gasummax. In this embodiment, three correlations (correlations represented by line L21, line L22, and line L23) corresponding to the integrated intake air amount upper limit gasumumax are illustrated, for example, the integrated intake air amount upper limit calculated in S103. It is assumed that the above correlation represented by the line L21 is selected based on gasummax.

Further, in the present embodiment, a control map in which the vehicle speed of the hybrid vehicle 100 is reflected in the throttle opening upper limit tamax based on the correlation represented by the selected line L21 (see FIG. 17B). Is prepared. If the vehicle speed of the hybrid vehicle 100 is high at the time of cold start of the internal combustion engine 10 in which this output suppression control is executed, even if the opening of the throttle valve 14 is the same as when the vehicle speed is low, it is inevitably necessary. In particular, the amount of intake air taken into the internal combustion engine 10 increases, which may lead to an increase in input energy to the EHC 1 via the exhaust gas. Therefore, in the control map shown in FIG. 17B, the correlation between the engine speed and the throttle opening upper limit tamax is set so that the intake air amount is further suppressed as the vehicle speed of the hybrid vehicle 100 increases. Yes. Specifically, when the vehicle speed EV = 0 km / h, the correlation indicated by the line L21-1 is set, and when the vehicle speed EV = 50, 90 km / h, the lines L21-2, L21- The correlation indicated by 3 is set. The control map shown in FIG. 17 (b) corresponds to the correlation related to the line L21 in FIG. 17 (a). Of course, the vehicle speed also applies to the correlation related to the line L22, the line L23, etc. A control map reflecting the above is prepared.

Thus, by using the control maps shown in FIGS. 17A and 17B, the throttle opening upper limit tamax determination processing in S301 is performed, and thereafter, the processing from S108 onward is performed. Thus, by performing the output suppression control shown in FIG. 16, when the internal combustion engine 10 is cold-started, the integrated intake air amount is changed in the carrier in the catalyst carrier 3 according to various parameters including the EHC temperature Tehc. The temperature difference ΔT is controlled so as not to exceed a limit value for preventing the temperature difference ΔT from excessively expanding. In particular, since the vehicle speed at the time of control is reflected on the upper limit value of the integrated intake air amount, it is possible to accurately avoid the increase in the temperature difference ΔT in the carrier even in the cold start of the internal combustion engine 10 from the soak state.

A fourth embodiment of the control apparatus for the internal combustion engine 10 according to the present invention will be described with reference to FIGS. FIG. 18 is a flowchart of control for suppressing the occurrence of cracks in the EHC 1 as a modified example of the exhaust air-fuel ratio control shown in FIG. 10, and the exhaust air shown in FIG. Processes that are substantially the same as the processes that constitute the fuel ratio control are given the same reference numerals, and detailed descriptions thereof are omitted. Specifically, the exhaust air / fuel ratio control shown in FIG. 18 is obtained by replacing the process of S201 of the exhaust air / fuel ratio control shown in FIG. 10 with S401.

Therefore, the process of S401 performed after an affirmative determination in S105 will be described. In S401, as in S201, the rich control amount of the exhaust air-fuel ratio is determined. In this embodiment, in addition to the engine speed and EHC temperature of the internal combustion engine 10, the hybrid at the time of this control is determined. The vehicle speed of the vehicle 100 is taken into account. Accordingly, the method for determining the rich control amount in S401 will be described based on FIG. In the present embodiment, the rich control amount is determined using the control map shown in FIG. 19A and the control map shown in FIG. The control map shown in FIG. 19A is substantially the same as the control map shown in FIG. 12 corresponding to the process of S201, and therefore detailed description thereof is omitted. Then, according to the control map shown in FIG. 19A, the correlation between the engine speed and the exhaust air / fuel ratio is selected based on the EHC temperature. In this embodiment, four correlations (correspondences represented by line L31, line L32, line L33, and line L34) according to the EHC temperature are illustrated, for example, represented by a line L32 based on the EHC temperature. It is assumed that the above correlation is selected.

Next, in the present embodiment, a control map (see FIG. 19B) in which the vehicle speed of the hybrid vehicle 100 is reflected in the rich control amount based on the correlation represented by the selected line L32. It is prepared. If the vehicle speed of the hybrid vehicle 100 is high during the cold start of the internal combustion engine 10 where the exhaust air-fuel ratio control is executed, even if the opening of the throttle valve 14 is the same as when the vehicle speed is low, Inevitably, the amount of intake air taken into the internal combustion engine 10 increases, which may lead to an increase in input energy to the EHC 1 via the exhaust gas. Therefore, in the control map shown in FIG. 19B, the correlation between the engine speed and the exhaust air / fuel ratio is set so that the exhaust air / fuel ratio shifts to a richer side as the vehicle speed of the hybrid vehicle 100 increases. Has been. Specifically, the correlation indicated by the line L32-1 is set when the vehicle speed EV = 0 km / h, and the lines L32-2 and L32- are respectively set when the vehicle speed EV = 50 and 90 km / h. The correlation indicated by 3 is set. The control map shown in FIG. 19 (b) corresponds to the correlation related to the line L32 in FIG. 19 (a), but of course the vehicle speed also relates to the correlation related to the line L33, the line L34, etc. A control map reflecting the above is prepared.

As described above, by using the control maps shown in FIGS. 19A and 19B, the rich control amount determination process in S401 is performed, and thereafter, the processes in and after S202 are performed. Thus, by performing the exhaust air-fuel ratio control shown in FIG. 18, the exhaust air-fuel ratio is changed according to various parameters including the EHC temperature Tehc when the internal combustion engine 10 is cold-started. Control is performed so that the internal temperature difference ΔT does not excessively increase. In particular, since the vehicle speed at the time of control is reflected in the rich control amount, it is possible to accurately avoid the increase in the temperature difference ΔT in the carrier even in the cold start of the internal combustion engine 10 from the soak state.

A fifth embodiment of the control apparatus for the internal combustion engine 10 according to the present invention will be described with reference to FIGS. FIG. 20 shows a case where power is supplied to the EHC 1 in advance before the internal combustion engine 10 is cold-started and its EHC temperature is raised, so that energy is input via exhaust during the subsequent cold-start. 5 is a flowchart of control for preventing the temperature difference ΔT in the carrier from excessively increasing in the catalyst carrier 3, and this control is referred to as pre-startup EHC energization control. The control is repeatedly executed as appropriate by the ECU 20 while the internal combustion engine 10 is stopped.

First, in S501, the EHC temperature Tehc is acquired. The estimation and calculation of the EHC temperature are performed based on the exhaust gas temperature detected by the temperature sensor 6a as shown in the above embodiments. Thereafter, in S502, the vehicle speed evspd of the hybrid vehicle 100 is acquired based on the value detected by the crank position sensor 11. When the process of S502 ends, the process proceeds to S503.

In S503, the target EHC temperature, which is a target temperature when the EHC 1 is energized in advance and the temperature thereof is increased in a state where the internal combustion engine 10 is stopped, that is, before the cold start of the internal combustion engine 10 is performed. tempev is calculated. This target EHC temperature tempev is preliminarily determined in advance at the time when exhaust gas flows so that the internal combustion engine 10 is cold-started and the exhaust gas flows into EHC 1 so that the temperature difference ΔT in the carrier that causes cracking does not increase excessively. It is set to keep the temperature raised. As the EHC temperature immediately after the cold start of the internal combustion engine 10 is higher, the temperature difference ΔT in the carrier is less likely to increase as shown in the above-described embodiments (for example, FIGS. 9B and 15B).

Therefore, the calculation of the target EHC temperature tempev is performed according to the control map shown in FIG. In the control map, the horizontal axis represents the vehicle speed evspd and the vertical axis represents the target EHC temperature tempev, which defines the correlation between the two. In the relative relationship, the target EHC temperature tempev is set to be higher as the vehicle speed evspd is higher. This is because if the internal combustion engine 10 is cold-started when the vehicle speed evspd is higher, more intake air is taken into the internal combustion engine 10, and as a result, more energy is input to the EHC 1 via the exhaust, In consideration of the fact that the temperature difference ΔT in the carrier is excessively increased, it is intended to suppress the expansion of the temperature difference ΔT in the carrier by setting a higher target EHC temperature. As described above, in S503, the target EHC temperature tempev is calculated based on the vehicle speed evspd acquired in S502, according to the control map shown in FIG. When the processing of S503 ends, the process proceeds to S504.

In S504, it is determined whether or not the EHC temperature Tehc acquired in S501 is higher than the target EHC temperature tempev calculated in S503. If an affirmative determination is made in S504, energization to EHC1 is not performed (processing of S505). On the other hand, if a negative determination is made, energization to EHC1 is performed so that the EHC temperature reaches the target EHC temperature tempev ( Process of S506).

If the pre-startup EHC energization control is performed in this way, the EHC temperature is based on the vehicle speed of the hybrid vehicle 100 while the internal combustion engine 10 is stopped, and the in-carrier temperature difference ΔT that causes cracks is generated. The temperature is controlled so as not to expand too much. Therefore, even if the internal combustion engine 10 is cold-started during the travel of the hybrid vehicle 100 thereafter, the generation of cracks due to the flow of exhaust gas into the EHC 1 can be suppressed.

1 .... EHC (electrically heated catalyst)
2 ... Exhaust passage 3 ... Catalyst carrier 4 ... Case 5 ... Matte 7 ... Electrode 10 ... Internal combustion engine 12 ... Intake passage 13 ...・ Air flow meter 14 ... Throttle valve 20 ... ECU
21a, 21b... Motor (motor generator)
30 ... Battery 100 ... Hybrid vehicle

Claims

An electrically heated catalyst that is provided in an exhaust passage of the internal combustion engine and heats a catalyst having exhaust purification ability with heat from a heating element that generates heat by supplying power;
When the internal combustion engine is cold-started, the electric heating type catalyst is supplied to the electric heating type catalyst so that the temperature difference between the predetermined parts of the electric heating type catalyst in the heating element is within a predetermined temperature range. A determining means for determining a suppression amount of input energy via the exhaust;
Control means for controlling the operating state of the internal combustion engine in accordance with the amount of suppression of the input energy determined by the determining means;
An internal combustion engine control device comprising:
The determining means is a predetermined parameter related to an exhaust amount flowing through the electrically heated catalyst so that the temperature difference in the heat generating body falls within the predetermined temperature range based on an elapsed time from a cold start of the internal combustion engine. An upper limit integrated value that is an upper limit value of the integrated value is calculated as a suppression amount of the input energy,
The control means prevents the actual integrated value of the predetermined parameter from the cold start of the internal combustion engine from exceeding or close to the upper limit integrated value calculated by the determining means. Controlling the engine output of the internal combustion engine;
The control apparatus for an internal combustion engine according to claim 1.
The predetermined parameter is an intake air amount in the internal combustion engine.
The control apparatus for an internal combustion engine according to claim 2.
The determining means is a predetermined parameter related to an exhaust amount flowing through the electrically heated catalyst so that the temperature difference in the heat generating body falls within the predetermined temperature range based on an elapsed time from a cold start of the internal combustion engine. An upper limit integrated value that is an upper limit value of the integrated value is calculated as a suppression amount of the input energy,
The control means prevents the actual integrated value of the predetermined parameter from the cold start of the internal combustion engine from exceeding or close to the upper limit integrated value calculated by the determining means. Adjusting the exhaust air-fuel ratio by fuel combustion in the internal combustion engine and controlling the exhaust temperature;
The control apparatus for an internal combustion engine according to claim 1.
The internal combustion engine is a spark ignition internal combustion engine,
The control means adjusts the combustion condition in the internal combustion engine so that the exhaust air-fuel ratio becomes richer as the actual integrated value of the predetermined parameter becomes larger, and lowers the exhaust temperature.
The control device for an internal combustion engine according to claim 4.
Estimating means for estimating or detecting the temperature of the electrically heated catalyst is further provided,
The determining means reduces the amount of suppression of input energy via exhaust to the electrically heated catalyst as the temperature of the electrically heated catalyst estimated or detected by the estimating means increases.
The control device for an internal combustion engine according to any one of claims 1 to 5.
Control of the operating state of the internal combustion engine according to the amount of suppression of the input energy by the control means is performed in a predetermined acceleration period immediately after the cold start of the internal combustion engine.
The control device for an internal combustion engine according to any one of claims 1 to 6.
The internal combustion engine is mounted on a hybrid vehicle having a power source of the internal combustion engine and a motor driven by power supplied from a power source,
The determining means increases the amount of suppression of input energy to the electrically heated catalyst as the vehicle speed of the hybrid vehicle at the cold start of the internal combustion engine increases.
The control device for an internal combustion engine according to any one of claims 1 to 7.
A control device for an internal combustion engine mounted on a hybrid vehicle having a power source of an internal combustion engine and a motor driven by power supplied from a power source,
An electrically heated catalyst that is provided in an exhaust passage of the internal combustion engine and heats a catalyst having exhaust purification ability with heat from a heating element that generates heat by supplying power;
When the hybrid vehicle is running using the motor as a power source with the internal combustion engine stopped, the electric heating catalyst is supplied with electric power to cause the heating element to generate heat before starting the internal combustion engine. Heating means before starting,
The pre-starting heat generating means is configured so that a temperature difference within the heat generating body, which is a temperature difference between predetermined portions of the heating element of the electric heating catalyst, falls within a predetermined temperature range even if the internal combustion engine is cold started. In addition, the electric heating catalyst is heated based on the vehicle speed of the hybrid vehicle to raise the temperature of the electric heating catalyst.
Control device for internal combustion engine.
The pre-starting heat generating means supplies power so that the temperature of the electric heating catalyst increases as the vehicle speed of the hybrid vehicle increases.
The control device for an internal combustion engine according to claim 9.